1. Field of the Invention
The present invention relates to a method of performing a uniform illumination pattern in a back-light plate. More specifically, the present invention relates to a method of performing a uniform illumination pattern in a back-light plate using sand-blasting.
2. Description of the Prior Art
The inner light source of a scanner or a liquid crystal display (LCD)comprises a fluorescent tube and a back-light plate to generate a back-light source, in order to scan a transparent document or to illuminate an LCD panel. Because the fluorescent tube is placed on one incident side of the back-light plate, the light emitted from the back-light plate is not uniformly distributed over the entire back-light plate, especially brighter in the area near the incident side of the back-light plate. In order to solve the problem of non-uniform illumination, the prior art teaches to make plural spots on the back-light plate. The purpose of these spots is to reflect the light from the incident side of the back-light plate, so the light emitted from the illuminating face can be uniform.
Please refer to FIG. 1. FIG. 1 depicts a top view of a back-light plate 10 of the prior art. The prior art back-light plate 10 is a substantially flat and transparent plate structure, which comprises two parallel illuminating faces, and a substantially linear tube 12 is placed on one incident side of the back light plate 10. There are plural spots 16 on one illuminating face 14 of the back-light plate 10. These spots form a uniform illumination pattern. The farther the spot is away from the tube 12, the bigger the spot is and the distance between the adjacent spots is shorter. On the contrary, the nearer the spot is from the tube 12, the smaller the spot is and the distance between the adjacent spots is longer. When a visible light illuminating from the tube 12 incidents into the back-light plate 10 via the incident side, the plural spots of various sizes and of different distances make the emitted light uniformly distributed over the entire back-light plate 10. The prior art methods of performing the uniform illumination pattern on a back-light plate are mainly divided into two kinds: the method of printing and the method of injection molding. The method of printing prints the spots 16 on the hard acrylic resin plate by manpower. Not only the cost is too high, but also the quality of printing is not easily under control. For example, the ink spreads when it is too much, the performance of printing is not uniform when the ink is not enough. And the ink is easy to absorb light, so that it can""t achieve the purpose of absolute reflection. As to the method of injection molding, it must fabricate a pattern mold according to the design of uniform illuminating pattern. It is not only expensive, but also leads to inconvenience when molds of different pattern design are to be fabricated. Due to the aforementioned problems, there is indeed an urgent need to develop different kinds of method to perform uniform illuminating pattern on a back-light plate, in order to reduce the cost of materials and manufacturing, and hereby enhance competence of the manufacturer.
It is therefore a primary objective of this invention to provide a method of performing a uniform illumination pattern in a back-light plate using sand-blasting. The present invention not only avoids the drawbacks in the prior arts, but also reduce the cost of materials, manufacturing, and their assembly.
According to the present invention, there is provided a method comprising steps of: (1) performing a manufacturing process to form a hole mask with a predetermined hole pattern; and (2) positioning the hole mask on one illuminating face of the back-light plate to perform a sandblasting process so as to form a plurality of recesses. After the aforementioned method is carried out, the recesses of uniform illumination pattern are formed on the back-light plate. When the visible light emitting into the back-light plate, the plurality of recesses on the illuminating face would make the emitted visible light uniformly illuminated so as to achieve its originally intended purpose.
It is an advantage of the present invention that, by means of the popular sand-blasting process, the uniform illumination pattern of the back-light plate can be performed in a simple and cost-effective method. By properly setting various parameters of the sand diameter, sand species, duration of performing the sand blasting process or force, etc, the depth of recesses are under control so as to optimize the effect of light uniformity of the uniform illumination pattern.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.